Completion liner delivery method with bridge plug capture

ABSTRACT

In an underbalanced or overbalanced completion, the packer that isolates a portion of the wellbore is preferably a composite mechanically set bridge plug. The composite materials are selected to expedite mill out the plug. A coring mill envelopes the plug as it cuts away the grip of the slips. Internal uphole oriented wickers inside the coring mill grab hold of it before the slip grip is lost to capture the plug in the coring mill. The liner string is rotated to operate the mill or alternatively a downhole motor can be used to run the coring mill. After the bridge plug is milled to a release and capture position, the liner string that can be slotted liner or screen or other tubular is advanced into position further down the usually deviated wellbore.

FIELD OF THE INVENTION

The field of the invention is downhole underbalanced completions where abridge plug has to be removed and a liner advanced in a single trip orin overbalanced conditions as a fluid loss device.

FIELD OF THE INVENTION

When wells are being drilled, it is always desirable to complete thewell including the bottom hole assembly liner in a manner so as tominimize the applied pressure on the formation. In essence, it isundesirable to apply excess pressure to the formation, known as killingthe well, during the completion process. In prior situations,particularly those involving deviated wellbores, the initial portion ofthe well is drilled and a casing is set. The casing is then cemented.After the cement sets, the deviated portion of the wellbore is drilled.Prior designs have involved running a liner string into the wellboreafter completion of the drilling of the deviation in the wellbore beyondthe cemented casing. An inflatable packer has been inserted through theliner string to isolate the formation while the bottom hole assembly isassembled into the wellbore above an inflatable bridge plug. However,certain problems have developed in particular applications with the useof through-tubing inflatable bridge plugs. For one thing, the ability ofthe through-tubing inflatables to hold particular differentials can beproblematic, especially if there are irregularities in the sealingsurface where the plug is inflated. Additionally, due to the compactdesign required in certain applications, the through-tubing inflatableelement cannot expand far enough to reliably hold the necessarydifferential pressures that may exist across the inflated bridge plug.Finally, there could also be difficulties in retrieval of thethrough-tubing inflatable bridge plug back through the string from whichit was delivered. The flexible nature of the through-tubing inflatabledesign could also create problems if it was decided simply not toretrieve the plug after putting together the bottom hole assembly aboveit. The slender design of the through-tubing inflatable plug couldcreate advancement problems if the plug were to be merely pushed to thebottom of the hole with the production tubing. If any washouts in thedeviated portion of the wellbore are to be encountered by the bottomhole assembly with the deflated through-tubing plug at the front, thenthe entire assembly may get stuck prior to its being advanced to thebottom of the wellbore for proper positioning. Generally, thethrough-tubing designs have not provided a circulation passagetherethrough to facilitate advancement of a deflated plug into theuncased portion of a wellbore using circulation.

More recently an inflatable bridge plug that is not through tubing hasbeen tried with the intent on deflating it with the advancing linerstring and capturing the deflated inflatable and moving the string intandem with the now deflated inflatable. This technique is illustratedin U.S. Pat. No. 5,749,419. However, there were issues with using thistechnique as well. The inflatable would lose grip or deflate. Thedeflated inflatable would not be cleanly captured and would tend to ballup to prevent forward progress of the liner string behind it. Sometimesthe deflated liner would simply release from the advancing string andprevent subsequent string advancement downhole. U.S. Pat. No. 6,915,858addressed some of these issues, most notably the tendency of thedeflated packer to wad up or swab as it was being advanced downhole. Theidea was to mechanically extend the deflated inflatable packer so thatthe tendency to swab would be reduced. While this design removed some ofthe issues in using inflatables for this application, it still leftothers unaddressed and various failure modes were still encountered.

The present invention moves away from efforts to use inflatables andinstead uses a non-inflatable. In the preferred embodiment, a compositemechanically set bridge plug is used and a core mill is brought down toit with a liner string behind the coring mill. The mill breaks loose theslip grip and retains the bridge plug as the string is then advanced.These and other benefits of the present invention will be more apparentto those skilled in the art from a review of the description of thepreferred embodiment and the associated drawings, which appear below,while recognizing that the scope of the invention is determined by theclaims.

SUMMARY OF THE INVENTION

In an underbalanced or overbalanced completion, the packer that isolatesa portion of the wellbore is preferably a composite mechanically setbridge plug. The composite materials are selected to expedite mill outthe plug. A coring mill envelopes the plug as it cuts away the grip ofthe slips. Internal uphole oriented wickers inside the coring mill grabhold of it before the slip grip is lost to capture the plug in thecoring mill. The liner string is rotated to operate the mill oralternatively a downhole motor can be used to run the coring mill. Afterthe bridge plug is milled to a release and capture position, the linerstring that can be slotted liner or screen or other tubular is advancedinto position further down the usually deviated wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing the composite bridge plug in place withslips set;

FIG. 2 shows the coring bit and liner assembly moving into mill outposition;

FIG. 3 is the view of FIG. 2 showing the bridge plug milled out andretained by the bottom hole assembly;

FIG. 4 shows the bottom hole assembly advancing toward the well bottombeyond the former position of the bridge plug;

FIG. 5 is an enlarged view of the mill shown in FIGS. 2-4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a well bore 10 that is lined with casing 12 and cemented14. The lower end 16 of the wellbore 10 is preferably open hole. Abridge plug 18 that is preferably made of composite (or mostlynon-metallic) materials is set in wellbore 10. The use of compositematerials allows a more rapid milling rate. The bridge plug is of aknown design and has upper slips 20 and lower slips 22 on either side ofa resilient sealing element 24.

FIG. 2 shows what happens in preparation for lining the lower end 16 ofthe wellbore. A drill string 26 supports a liner hanger 28 that islocated above a liner string 30. A float collar 32 is within linerstring 30. At the lower end 34 is a coring mill 36 that is shown in moredetail in FIG. 5. The mill 36 has circumferential cutters 38 that aresized to encounter the slips 20 and 22 to break loose their grip. As thecoring mill 36 descends when cutting the slips 20 and 22 the bridge plugenters the core 40 and comes into a gripping device that still permitsfluid flow around the now captured plug 18, as also shown in FIG. 3. Thecoring mill 36 can be operated by rotation of the drill string 26.Alternatively a downhole motor (not shown) can be attached to the drillstring 26 so that only the bottom hole assembly below the downhole motoractually rotates. Alternatively, the drill string 26 can be rigid orcoiled tubing.

Referring to FIG. 5, the gripping device for the bridge plug 18 can be aseries of circumferential wickers that are preferably oriented uphole toretain the bridge plug 18 after the mill descends enough to capture itin wickers 42. Preferably, the wickers are in spaced segments that leavelongitudinal passages 44 to allow flow around the captured bridge plug18 when retained by wickers 42. The passages 44 allow cooling fluid thatis circulated into core 40 to cool the cutters 38 as milling continues.Circulation can be continued while the assembly is then lowered furtherin the wellbore 10 into position at the lower end 16, as shown in FIG.4.

Those skilled in the art will appreciate that the problems with prioruses of inflatables have been eliminated with the present invention. Themilling rates are high due to the use of composite materials in thepreferred bridge plug. While small pieces that are formed in the millingprocess can be circulated to the surface, the bulk of the body of thebridge plug 18 is retained within core 40 at the conclusion of themilling. The retention devices can be varied although uphole orientedwickers are preferred. Magnets can also be employed to capture magneticparts, if any. Retention of the milled out packer can continue even withcirculation through the core 40 as the liner 30 is advanced to reducethe risk of hanging up during the advance. As an alternative the bridgeplug can be mechanically released rather than milled. It is preferred toretain the released bridge plug in a core for the trip downhole evenwhen the release is accomplished mechanically as opposed to by milling.Additional provisions can be incorporated into the retention device forthe spent bridge plug to release it to the bottom of the hole ifrequired. This can be done with circulation or through articulatedgrippers that can fully release it or even extend it out past the core40 so it can be reset by mechanical manipulation, pressure or othertechniques. Alternatively, if the bridge plug is of a resettable designit can be moved downhole and extended from the core 40 and reset abovethe hole bottom.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below.

1. A downhole completion assembly comprising: a non-inflatable plugsettable in a wellbore to isolate one portion of the wellbore fromanother; a release tool supported from a string and designed to releasesaid plug and retain it as said string is further advanced downhole. 2.The assembly of claim 1, wherein: said release tool comprises aninternal core to at least in part retain said plug after its release. 3.The assembly of claim 2, wherein: said release tool mills said plug. 4.The assembly of claim 3, wherein: said plug comprises at least one slipmilled out by said release tool.
 5. The assembly of claim 2, wherein:said plug comprises a slip that is mechanically released by saidreleasing tool.
 6. The assembly of claim 2, wherein: said core comprisesa retaining member to hold said plug after its release.
 7. The assemblyof claim 2, wherein: said core defines at least one bypass passage toallow flow around said plug when retained in said core.
 8. The assemblyof claim 6, wherein: said retaining member comprises a plurality ofwickers oriented in the opposite direction from movement of the releasetool that brings said plug into said core.
 9. The assembly of claim 8,wherein: said retaining member defines at least one flow passage runningalong said wickers.
 10. The assembly of claim 2, wherein: said plug isreleasable from said core after its retention therein.
 11. The assemblyof claim 2, wherein: said plug is extendable from said core after beingretained therein.
 12. The assembly of claim 11, wherein: said plug isresettable after being extended from said core.
 13. The assembly ofclaim 3, wherein: said plug is made of substantially non-metallicmaterials.
 14. The assembly of claim 13, wherein: said plug is made ofsubstantially composite materials.
 15. The assembly of claim 3, wherein:said release tool is operated by string rotation from the surface of thewellbore.
 16. The assembly of claim 3, wherein: said release tool isoperated by a downhole motor mounted in said string.
 17. The assembly ofclaim 2, wherein: said string further comprises a hanger.
 18. Theassembly of claim 17, wherein: said string comprises openings forsubsequent production.
 19. The assembly of claim 17, wherein: saidstring comprises a float collar.
 20. The assembly of claim 2, wherein:said plug comprises upper and lower slips with a sealing element inbetween and a substantially non-metallic body; said release tool millingsaid slips as it captures said body in said core.